Abstract

Future implementation of regenerative treatments for sensorineural hearing loss may be hindered by the lack of diagnostic tools that specify the target(s) within the cochlea and auditory nerve for delivery of therapeutic agents. Recent research has indicated that the amplitude of high-level compound action potentials (CAPs) is a good predictor of overall auditory nerve survival, but does not pinpoint the location of neural damage. A location-specific estimate of nerve pathology may be possible by using a masking paradigm and high-level CAPs to map auditory nerve firing density throughout the cochlea. This initial study in gerbil utilized a high-pass masking paradigm to determine normative ranges for CAP-derived neural firing density functions using broadband chirp stimuli and low-frequency tonebursts, and to determine if cochlear outer hair cell (OHC) pathology alters the distribution of neural firing in the cochlea. Neural firing distributions for moderate-intensity (60 dB pSPL) chirps were affected by OHC pathology whereas those derived with high-level (90 dB pSPL) chirps were not. These results suggest that CAP-derived neural firing distributions for high-level chirps may provide an estimate of auditory nerve survival that is independent of OHC pathology.

Received 16 December 2010Revised 20 October 2011Accepted 25 October 2011Published online 13 January 2012

Acknowledgments:

This research was funded by The Royal National Institute for Deaf People (Action on Hearing Loss), United Kingdom. The authors thank John Ferraro, Judy Widen, Tiffany Johnson, Thomas Imig, and three anonymous reviewers for their helpful comments on an earlier version of this manuscript. The authors also thank Ashlee Martz and Megan Ash for their assistance with data collection.

Key Topics

[Methods or devices for transmitting, conducting or
directing sound in general; Methods or devices for protecting against, or for damping,
noise or other acoustic waves in general, Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general]